The present invention generally pertains to telecommunications and is particularly directed to subscriber communicators.
One subscriber communicator known as the ORBCOMM subscriber communicator is adapted for use in the ORBCOMM Satellite communication network. The ORBCOMM network includes twenty-eight low-earth-orbit (LEO) communication satellites, gateway Earth stations, network control centers and a global network operations center in Dulles, Va. The ORBCOMM network provides wireless, two-way global satellite data communications between mobile subscriber communicators and operators via the Internet or dedicated leased lines for high-volume operations. ORBCOMM downlink signals are provided in a symmetrical differential phase-shift-keyed (SDPSK) format at 4800 bps in receive frequency range between 137.0 and 138.0 MHz. ORBCOMM uplink signals are provided in a SDPSK format at 2400 bps in transmit frequency range between 148.0.0 and 150.05 MHz.
The ORBCOMM subscriber communicator includes an RF section for receiving RF communication signals, for converting the received RF signals to digital output samples and for converting digital input samples to RF communication signals for transmission; a transformation section for transforming the digital output samples to digital output data and for transforming digital input data to the digital input samples; and a control processing section for processing digital data in accordance with ORBCOMM data protocols to provide a plurality of communication activities that facilitate various user applications, such as telematics, industrial controls, and set-top boxes.
Each of the RF section, the transformation section and the control processing section includes both hardware and software elements. The transformation section includes a digital signal processor (DSP). The processing section typically includes a multi-functional microprocessor, such as a Motorola 68040. The performance of each of these three sections is implemented by software. All three of these sections and the respective implementing software are contained in one module.